Documents, such as identification cards, credit cards, banking cards, driver's licenses, some banknotes, security documents, security cards, etc may be formed from microporous material and multilayer articles comprising such microporous material. Marking of these documents with identification marks, such as date codes, batch codes, bar codes, images, text, functional marks, such as computer keyboard characters, and decorative marks, is common practice to deter forgery and allow counterfeit documents to be readily detected. Laser marking or engraving is a well known means for quickly and cleanly inscribing these identification marks on and within such documents.
Using a laser to provide a document with written or engraved information has a number of advantages over conventional ink printing. For example, using a laser to provide an engraving that has a tactile feel can be a useful authenticator of data that can be difficult to counterfeit or alter. In addition, laser engraving generally does not require the use of ink, which can reduce the cost of consumables used to manufacture such documents. Laser engraving can also be more durable than ink printing and more resistant to abrasion, which can be useful if a counterfeiter attempts to rub off ink-applied information. The resolution and print quality provided by laser engraving typically is better than that of conventional ink-based printing. The laser engraving process also can be a more environmentally friendly marking process than printing with ink because solvents and other chemicals associated with printing inks are not used.
Despite the advantages of using a laser to engrave information on a document and thereby inhibit counterfeiting or altering of the document, some types of materials do not produce adequate contrast and/or resolution of the engraved information when engraved with a laser. Additionally, while some materials, such as polycarbonate, may provide adequate contrast and/or resolution when laser-marked, such materials may not be readily “printable” using a wide range of printing techniques. Therefore, there is a need in the industry for a readily printable material, such as microporous filled polyolefin material, which provides adequate contrast and/or resolution when laser-marked.